It is frequently necessary to burn gas at oil and gas installations. The gas is typically directed to a vertically standing pipe or flare stack. Gas exiting the top of the pipe is ignited with an igniter. It is important that the gas be kept burning. With high winds, the flame can easily be blown out. As a result, high gas flow rates may be required to keep the flame alive. As pressure varies within the flare stack, the flow rate of gas may vary. When the flow rate is low, the flame is more easily blown out. Kaldair of Houston, Tex., has provided a device which uses the Coanda effect and a pot valve to variably control the flow of gas from the flare stack in response to variation of pressure within the stack. While this device has had commercial success, the inventor has provided an improvement upon it.